This study will examine the effectiveness of the drug pirfenidone (Deskar) in improving heart function in patients with hypertrophic cardiomyopathy (HCM). Stiffening of the heart muscle in patients with HCM impairs the heart's ability to relax and thus fill and empty properly. This can lead to heart failure, breathlessness and excessive fatigue. The heart's inability to relax may be due to scarring, or fibrosis, in the muscle wall. This study will test whether pirfenidone can reduce fibrosis, improve heart relaxation and reduce abnormal heart rhythms.